The goal of the proposed research is to obtain basic information on how maternal diet and nutrition affect the composition of milk and the health of the neonate. The proposal focuses on the delivery of vitamin A (retinol) from mother to young during pregnancy and lactation. Specific goals are: 1) to understand how diets that differ widely in fat and/or protein content affect retinol transport in milk and neonatal stores of vitamin A; 2) to understand how acute supplementation with retinyl acetate or Beta-carotene to pregnant or nursing rats fed a basal vitamin A diet changes milk vitamin A content and whether acute supplementation will significantly expand the weanling's liver stores of vitamin A; 3) to explore whether expanded liver and body stores of retinol have functional effects on growth or the ability of the neonate to respond immunologically to an antigen challenge, and 4) to obtain a comprehensive profile of the levels of retinol and its transport protein retinol-binding protein (RBP), as well as transthyretin (TTR) in serum of animals from pre-pregnancy through lactation. We also plan to investigate possible differences in the molecular form of the vitamin A transport complex in the adult and fetal animal. In all studies, semisynthetic diets will be fed to control the content of vitamin A, fat and protein, and food consumption will be monitored. Sensitive assays will allow measurement of retinol concentrations, retinyl ester patterns and fatty acid profiles in milk samples collected from day 1 to near the end of lactation. Immunoassays will be used to measure specifically the levels of RBP and TTR in serum of dams or pups. Possible changes in the size and characteristics of the retinol transport complex during gestational development will be explored using gel permeation chromatography, electrophoresis, and immunoassays. Because vitamin A is essential for reproduction, growth, and normal differentiation of epithelia, it is essential to understand the effects of maternal nutrition and the mechanisms that regulate the transport of this nutrient from mother to young during gestation and lactation.